DESCRIPTION: The goal of this project is to determine if alterations occur in expression of different nucleotide excision repair enzymes during aging. Our preliminary evidence indicates that at least one of these DNA repair enzymes, ERCC3 or the p89 DNA helicase of the BTF2 transcription complex, is down regulated in vitro whereas another ERCC1 enzyme is not. Interestingly, the ERCC3 gene product is implicated in Cockayne's syndrome, considered by some to be a "premature aging" syndrome, whereas ERCC1 is not associated with Cockayne's or Xeroderma pigmentosum. Alterations in basal expression of other ERCC enzymes, and several other enzymes associated with DNA repair and transcription, will be determined both in vitro and in vivo. The in vitro studies involve monitoring mortal human diploid cells as the cells senesce. The in vivo studies involve comparing expression between a younger (20-30 years) and an older (>70 years) human population. The ability of these enzymes to respond to stress induced by different DNA damaging agents will also be compared in a younger versus older population. As the ERCC3/p89 helicase is only 1 of 5 components of the BTFII complex, he will also monitor the other 4 components. The second phase of the project will involve expressing specific ERCC/XP enzymes in human fibroblasts and determining if in vitro life span is altered. The final phase of the project involves isolating the murine homologue of ERCC3 (the one known to be down regulated), then producing mice overexpressing the ERCC3/p89 helicase to determine if alterations occur in either the mean (50%) or the maximum (95%) life span.